docs: def _get_distance_scaling(self, C, dists, mag):
          """
          Implements the distance scaling function F(M, R) presented in equations
          2 and 3. In the case of Joyner-Boore distance then the fixed-depth
          term h is required
          """
          r_h = self._get_rh(C, dists)
          return (C["c1"] + C["c2"] * (mag - self.CONSTANTS["mref"])) *\
              np.log(r_h / self.CONSTANTS["rref"]) +\
              C["c3"] * (r_h - self.CONSTANTS["rref"])